NET, IAS, State-SET (KSET, WBSET, MPSET, etc.), GATE, CUET, Olympiads etc.: Identification of Sedimentary Rocks
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Hardness | Grain Size | Composition | Other | Rock Type |
hard | coarse | clean quartz | white to brown | Sandstone |
hard | coarse | quartz and feldspar | usually very coarse | Arkose |
hard or soft | mixed | mixed sediment with rock grains and clay | gray or dark and “dirty” | Wacke/Graywacke |
hard or soft | mixed | mixed rocks and sediment | round rocks in finer sediment matrix | Conglomerate |
hard or soft | mixed | mixed rocks and sediment | sharp pieces in finer sediment matrix | Breccia |
hard | fine | very fine sand; no clay | feels gritty on teeth | Siltstone |
hard | fine | chalcedony | no fizzing with acid | Chert |
soft | fine | clay minerals | foliated | Shale |
soft | fine | carbon | black; burns with tarry smoke | Coal |
soft | fine | calcite | fizzes with acid | Limestone |
soft | coarse or fine | dolomite | fizzing with acid unless powdered | Dolomite rock |
soft | coarse | fossil shells | mostly pieces | Coquina |
very soft | coarse | halite | salt taste | Rock Salt |
very soft | coarse | gypsum | white or pink | Gypsum |
Sedimentary rocks are the second great rock class. Whereas igneous rocks are born hot, sedimentary rocks are born cool at the Earth՚s surface, mostly under water. They usually consist of layers or strata, hence they are also called stratified rocks. Depending on what they՚re made of, sedimentary rocks fall into one of three types.